Backpack



FIG. 1 is a front perspective view of a backpack showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a side view thereof;

FIG. 5 is an opposite side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The uneven-length broken lines represent unclaimed boundaries of the claimed design. The even-length broken lines showing the remainder of the backpack represent unclaimed subject matter and form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 